Scanning mechanisms are used in electronic printers and similar devices. In printers the scanning mechanism typically deflects a light beam, often a laser light beam, from a light beam source onto an imaging surface. Generally one or more mirror surfaces are used to deflect the light beam from the light beam source to the imaging surface. Typically the mirror surface moves in a periodic pattern to deflect the light beam across the imaging surface in a scanning motion. Drive electronics are generally used to control the motion of the mirror surface. The imaging surface may be an electrophotographic drum, a photographic film, a display, or other surface. The imaging surface generally combines successive scans of the light beam in order to form a visual or an electronic image.
It is generally desirable to have the light beam scan the imaging surface with a beam moving as a linear function of time (i.e., a constant velocity). This is often difficult to achieve because (1) the natural motion of the mirror surface may be intrinsically non-linear, and/or (2) the distance from the source of the beam to the imaging surface may change (due to the geometry of the optics, or other factors) as the beam scans the imaging surface. Often one or more compensating lenses or reflectors are used to help achieve linearity in the scanning motion. In addition to achieving linearity of the scan, the compensating lenses or reflectors typically also focus the light beam to a small spot along the scan path on the imaging surface. If one could have the ability to shape the scan pattern independently from the compensating lens, the compensating lens design could favor other performance factors such as spot size or uniformity, which may otherwise be compromised by the need to also address linearity with the same elements. In summary, what is needed is an apparatus and method to control the motion of a light beam in a scanning apparatus that is substantially independent from elements that may be used for enhancing other features of the light beam.